Laser Research, And The Role Of Characteristics Of Biological Tissue And Thermal Effects

With the increasing use of laser in life science such as biology and medicine, it is increasingly important to study the interaction of laser and bio-tissue. This paper just studies the thermal reaction according to the premise mentioned. The analysis is based on energy in this paper. In the first part, viewing the tissue as turbid media, the paper works out the radiative transport equation. Dividing the incident radiance into the reduced incident intensity L,, and the diffuse intensity Ld, this part works out the diffuse equation, the diffuse flux equation, the equation of the average diffuse intensity, boundary conditions and the solution of the diffuse equation based on a collimated beam incident upon a slab of particle. In the second part, the paper analyzes the migration and absorption of photon, works out the diffuse equation of photon in tissue and the time resolved reflectance and transmittance of tissue optical properties based on a short laser-light pulse. In the third part, this is the best important part. In this part, this paper analyzes the distribution of light in tissue based on the transport equation, the thermal response in tissue based on the light distribution, and analyses the temperature elevation distribution in tissue when the temperature reaches equilibrium. At last, this paper analyses the temperature distribution in tissue irradiated by a short pulse laser. This part analyses the removal of tissue using the temperature distribution too, to obtain the relations of the laser power density p. the laser pulse width t0, the depth of carved tissue z0, the size of the laser focal point D and the velocity of motion of tissue v.